Understanding What Fish Is Not White Meat: The World of Oily and Dark-Fleshed Fish

December 23, 2025 •

4 min read

Not all fish have white meat, with some species like tuna and salmon featuring distinctively darker flesh due to higher levels of myoglobin and fat. This difference is influenced by factors like diet and swimming habits, which determines what fish is not white meat.

Quick Summary

Dark-fleshed fish like tuna, salmon, and mackerel are not white meat, a result of higher myoglobin content and diet. These oily fish also contain higher levels of omega-3 fatty acids, affecting both flavor and nutritional profile.

Key Points

Myoglobin Content: The primary reason some fish have non-white meat is the presence of myoglobin, an oxygen-storing protein that gives muscle a darker color.
Oily Fish: Oily, active fish like tuna, salmon, mackerel, and herring are not white meat and contain significantly more omega-3 fatty acids than whitefish.
Diet and Color: The pink color in salmon is a result of their diet of krill and crustaceans containing carotenoid pigments.
Nutritional Density: Dark meat fish tend to be richer in healthy fats, vitamin D, and B vitamins, but some larger species may have higher toxin levels.
Spoilage Factor: The higher fat content in dark meat fish means it is more susceptible to spoiling faster than whitefish.
Flavor and Texture: Non-white fish typically have a richer, more intense flavor and a firmer texture compared to the mild, flaky texture of whitefish.

The Science Behind Fish Flesh Color

Fish flesh color is not a random trait but a direct reflection of a fish's biology, diet, and behavior. Unlike poultry, where red and white meat come from different muscle groups, the coloration in fish is determined primarily by the presence of a protein called myoglobin. Myoglobin is an oxygen-storing protein that gives muscle a reddish or darker color.

Fish that are constantly active and travel long distances, such as tuna and mackerel, require a higher oxygen supply to their muscles. As a result, their muscles contain more myoglobin, resulting in darker, more intensely colored flesh. Conversely, sedentary fish, like cod and sole, rely on short, fast bursts of energy and have much lower myoglobin content, hence their characteristically white flesh.

Diet is another crucial factor, especially for fish like salmon. The pink-orange hue of salmon comes from their consumption of crustaceans and other organisms rich in carotenoid pigments, such as astaxanthin. These pigments are then stored in the fish's fatty tissues. For instance, farmed salmon are often fed a diet with added astaxanthin to achieve the color consumers expect. Some species, like some King Salmon, are genetically unable to process these pigments, resulting in rare "ivory" or white-fleshed individuals.

In many fish fillets, you may also notice a thin, dark line of muscle running along the backbone, often called the "bloodline". This is the richest source of myoglobin and can have a stronger, more intense flavor than the surrounding white flesh.

Examples of Non-White Meat Fish

Oily, Dark-Fleshed Fish

Salmon: Known for its distinctive pink-to-reddish-orange flesh, salmon is one of the most popular examples of a non-white meat fish. Its oily nature and rich flavor are prized globally.
Tuna: Bluefin and Yellowfin tuna have a deep red, almost beef-like appearance when raw, due to their highly active swimming lifestyle. Albacore, while still an oily fish, is a notably lighter-colored variety.
Mackerel: A highly active swimmer with dark, oily flesh. The intensity of its color can vary based on the season and its activity levels.
Sardines and Herring: These small, schooling fish have rich, dark, and oily flesh. They are packed with flavor and nutrients.
Trout: While some farmed trout can be paler, wild trout often have pinkish flesh due to their diet, similar to salmon.

Other Non-White Varieties

Red Snapper: This fish has a beautiful pinkish flesh when raw that fades to white upon cooking. It is still generally considered a lean, white fish, but its raw color distinguishes it.
Mahi-Mahi: Also known as dolphinfish, this fish has pinkish-colored flesh that cooks up white.

Nutritional Profile: Dark Meat vs. White Meat Fish

The difference in flesh color is also indicative of a significant nutritional difference. The higher fat content in dark, oily fish is a source of important nutrients not as abundant in whitefish. Here is a comparison:


Feature	Dark Meat Fish (e.g., Salmon, Tuna)	White Meat Fish (e.g., Cod, Haddock)
Fat Content	Higher fat content, rich in unsaturated fats.	Lower fat content, making it leaner.
Omega-3 Fatty Acids	Excellent source of heart-healthy Omega-3s (EPA and DHA).	Lower levels of Omega-3s.
Vitamins	Generally richer in fat-soluble vitamins, such as Vitamin D and A.	Richer in B vitamins like B12.
Minerals	Often higher in minerals like iron and zinc.	Contains essential minerals, but generally less than dark meat.
Flavor	Richer, more intense flavor due to higher fat and myoglobin.	Milder, more delicate flavor.
Texture	Firmer and denser texture.	Light, flaky, and tender texture.

It is important to note that while dark meat fish offers more omega-3s, some larger, longer-living predatory species (like some large tuna) can accumulate higher levels of environmental toxins like mercury. It is recommended to eat a variety of fish to balance nutritional intake and minimize risk. For more information on fish and shellfish nutrition, consult official sources like the NHS: https://www.nhs.uk/live-well/eat-well/food-types/fish-and-shellfish-nutrition/.

Cooking and Flavor Differences

The higher fat content of dark meat fish makes it particularly moist and flavorful, but also means it is less forgiving if overcooked. Its richness pairs well with acidic or spicy flavors that can cut through the oiliness. Baking, broiling, and grilling are all excellent cooking methods that can handle the robust flavor and texture.

White meat fish, by contrast, has a delicate flavor and texture, which is why it often shines in simple preparations. It cooks quickly and is best prepared with light cooking methods like steaming, pan-searing, or poaching.

Conclusion

Understanding what fish is not white meat is a journey into the fascinating biology and nutritional diversity of seafood. The differences in color and fat content are primarily due to factors like a fish's activity level and diet. Rather than viewing one type as superior, it is better to appreciate the unique qualities of both. Dark, oily fish offers a nutrient-dense and flavorful experience, while whitefish provides a lighter, leaner option. By incorporating both into a balanced diet, you can enjoy a wide array of flavors and health benefits the ocean has to offer.

Frequently Asked Questions

The color of fish flesh is primarily determined by myoglobin, a protein that stores oxygen in muscles. Fish that are highly active, like tuna, need more oxygen and therefore have higher myoglobin levels, resulting in darker flesh.

No, salmon is not considered red meat. While its flesh is reddish-pink, this color comes from pigments in its diet (carotenoids from crustaceans), not from the same high level of heme that defines red meat from mammals. It is classified as an oily fish.

Not all types of tuna are red meat. While species like Bluefin and Yellowfin have dark red, beef-like flesh, Albacore tuna is an exception and has distinctly white flesh.

Dark meat fish, like salmon and tuna, often have a more nutrient-dense profile, particularly offering more heart-healthy omega-3 fatty acids, vitamin D, and B vitamins. However, both types of fish are nutritious and offer different benefits.

The pink-orange color in salmon is caused by astaxanthin, a carotenoid pigment found in the small crustaceans, like krill, that they eat. Farmed salmon are often given this pigment in their feed to achieve a similar color.

Yes, dark meat fish tends to spoil faster than white meat fish due to its higher fat content. The fats are more prone to oxidation, which can cause the fish to develop off-flavors and become rancid more quickly.

Yes, both swordfish and mackerel are considered dark meat. They are highly migratory, active swimmers that require high levels of oxygen, leading to higher myoglobin concentrations and darker, firmer flesh.

The dark strip, or "bloodline," running along the backbone of some fish fillets is a section of muscle with a very high myoglobin content. It is perfectly safe to eat, though some find its stronger flavor unappealing and choose to remove it.